Process for cooling rails



2 'Sheets-Sheet 1 R. B. GERHARDT PROCESS EOR COOLING RAILS Filed Dec. 5,193] Dec. 7, 1937.

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Fmmqf Dec. 7, 1937. R. B. GERHARD-r 4 `PROCESS FOR COOLING RAILS 2`sheets-sheet 2 Filed Dec. 5, 193] Cltrmwaf/ Patent PRGCESS 1F63 @GGGReald llt. Gerhardt, Steelton, a., gnor to Beth-Mary Steel Coration, acorporation of Maryland Application December 5, 1931, Serial No. 579,316

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My invention relates to a process for cooling rails in such manner thatdangerous stresses and strains are prevented in the rail metal.

An important problem in the manufacture of 5 rails at the present timeis the avoidance of stresses and strains in the metal which may developinto dangerous rail defects such as, for example, transverse or similarssures. Among the causes which may introduce dangerous stresses in therail metal, it has been suggested that a primary factor may be theconditions under which the rail is cooled. If, in cooling, substantialdiierences in temperature occur between the various parts of the rail,as say between the web and anges and the head, or between the interiorand exterior portions, particularly of the head, these temperaturedierences may give n'se to stresses which in turn may produce strainswhich ultimately may lead to the production of dangerous defects in therail structure.

It has vbeen proposed that the rails be slowly cooled through a range oftemperature extending from about 500 C. to 350 C., the thought beingthat this range is a danger zone and that if substantial differences oftemperature occur between the djierent portions o the rail while passingthrough such range, permanent defects of structure may ensue. In such aprocess the rail, while 'fl to conditions to provide a slow coolingthrough the alleged danger zone. Obviously in such processes to preventthe occurrences of substantial temperature dierences between the variousparts of the rail in the temperature range 500 to 350 C. it is usuallyimportant to begin the slow cooling at a temperature appreciably inexcess of 500 C. It will be readily apparent that in doing this there issome likelihood of producing more or less soitening of the rail becauseof the more or less elevated temperatures at which the rail is held.

I have discovered that while it is important to effect a slow cooling ofthe rail at a certain stage the retardation of cooling should take placeat a lower temperature. I have found that the important thing is toeiect a protracted cooling between 300 and 200 C. The cooling of therail prior to 300 C. may be of the ordinary character such as commonlytakes place on the hot bed' or it may be greatly accelerated as in thecase where it is desired to eiect a hardening of the rail to produce 'aheat treated rail. But whether cooled rapidly or at the normal rate I ndit important to subject the rail to a protracted cooling through therange 300 C. to 200 C., preferably irom 300 C. down to a temperature notstill at a temperature above 500 C., is' subjectedA (ci. 14a-2i) greatlyin oxces of ordinary atmospheric temperatures.

My invention comprises the cooling of a rail from above the criticalrange to a temperature less than 500 C. in the normal way on the hot 5bed, or by an accelerated cooling, and then placing the rail in closedcontainers before the temperature has dropped as low as 300 C. and cooling lslowly either to approximately atmospheric temperatures or to asomewhat higher tempera- 10 ture, but not higher than 200 C.

I shall rst describe an example of my process applied to the preparationof ordinary or unheat treated rails. The rails from the mill are run onto the hot bed in the usual way, the temperature of course then beingwell above the critical range. lI`hey are allowed to cool on the hot bedin the usual way until the temperature of a consequential portion of themetal of the rail head has dropped below 500 C. Without allowing the 20temperature of the major mass of the head of the rail to drop below 300C. the rails are then placed in more or less close proximity to eachother in containers which are closed and the rails allowed to cool toapproximately atmospheric 2g, temperature. The important range oftemperature ior this slow cooling is between 300 and 200 C. In practiceI ordnarily'allow the rails to remain in the chamber until thetemperature of the head of the rail has dropped to 50 to 75 C. 3@ whenthey are then removed. Preferably the temperature of the exterior of thehead of the rail ranges between 325 and 400 C. when placed in the closedchamber.

A suitable chamber for this purpose is shown 35 in the accompanyingdrawings. Referring to these drawings:

Fig. 1 is a 'plan view of this structure; and

Fig. 2 is `a cross section therethrough taken on the line 2-2 of Fig. 2.

The chamber is comprised of the masonry walls lli covered by roof i2,the front and back walls being of unequal height to give the structurean inclination downwardly from the rail receiving end to the raildelivery end. Inclined skids i3 5 mounted on pedestals i4 within thechamber project at their ends from the front and rear. At the rear of`the structure are inwardly swinging doors l5 and at the forward end areplvotally mounted outwardly swinging doors I6. At the 50 ,rear of thefurnace chamber are relatively short skids l1 plvotally connected to thepistons of hydraulic cylinders I8. 'Ihe forward ends oi these skids areplvotally connected by means of rods 2n to skids I3.

The rails are received from the hot bed on skids I 1 while such skidsare in the horizontal position. To charge the rails into the slowcooling chamber, the cylinders I8 are actuated to elevate skids Il, andrails I0 are discharged onto the projecting ends of skids I3. The railsare then pushed into the chamber through swinging doors l5. After thechamber has been lled with rails the addition of further rails causesthe discharge of rails from the forward side of the chamber throughswinging doors I6 into receiving cradles 2|.

`I shall now briefly outline a process, involving the principles of myinvention, for the production of a heat treated rail. While the majormass ot the rail is still above the critical point it is immersed inwater, oil or other suitable quenching medium and cooled rapidly throughthe critical range. This quench is of such duration that the temperatureof the major mass of the metal does not cool to the blue heat zone, butis preferably 0i' such a degree as to cool at least substantialproportions of the rail head metal to a temperature less than 500 C. vIffor any reason it is important that the quench be insufliciently drasticto lower the temperature of a substantial proportion of the head metalbelow 500 C., the rail is allowed to cool to a temperature below thispoint on the hot bed or in any other suitable location. When thetemperature of the exterior is appreciably below 500 C. but with themajor mass of the interior metal still above 300 C. the rails are placedin a suitable closed container to cool slowly through such temperaturerange as to include the range 300 to 200 C. A suitable device for thispurpose may be the oven or hood shown in the drawings and alreadymentioned in connection with a normally treated rail.

In carrying out the process for the heat treatment of rails, followingthe quenching operation, the temperature of the rail may be equalizedbefore being subjected to the slow cooling in the closed chamber. Forexample, the rails following the quench may be placed in a furnace whichis artificially heated andthe temperature of the rail equalized. Therail may remain in such a furnace for a substantial period of time toeffect a drawing action, to eliminate strains due to the quenchingoperation. From this furnace the rails may then pass to the closedchamber for effecting the slow cooling operation through the range 300to 200 C. It will be noted in vboth of the examples of my process givenabove the'rails are subjected to a relatively rapid cooling until atemperature of the rail has been obtained. less than 500 C. and thenbefore the temperature of the rail. or the major portion thereof, hasdropped to 300 C. placing in a closed chamber for eilecting a slowcooling to a temperature at least as low as 200 C.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. In a process for cooling a rail, the steps of cooling the rail at thenormal rate on the hot bed through the critical range, placing the railsin a closed chamber after a substantial part of the metal of the head ofthe rail has been lowered to less than 500 C. but before the temperatureof the major mass of the metal of the head has cooled as low as 300 C.and cooling slowly therein to approximately atmospheric temperature.

2. In a process for cooling a rail from above the critical range, thesteps of cooling therail in the normal way on the hot bed until asubstantial part of the metal of the head of the rail has been droppedbelow 500 C., placing the rail in a chamber before the temperature ofthe major mass of the head of the rail has dropped as low as 300 C., andcooling the rail slowly therein to a temperature less than 200 C.

3. In a process for treating a rail, the steps of quenching the railthrough the critical range and then after the temperature of the railhas been lowered to less than 500 C., but before it has been cooledbelow 300? C., placing in a closed chamber and cooling slowly to atemperature below 200 C.

4. A process for cooling rails from the original mill heat comprisingthe steps of cooling the rails from a temperature above the criticalrange at a. rate at least as rapid as that which normally occurs on thehot bed until the temperature of the rails is substantially below 500C., and after such cooling but before the major mass of the head metalhas cooled below 300 C. from the original mill Aheat enclosing the railsand cooling slowly Y through a temperature range which includes anextended range below 300 C. to prevent the development of those stressesand strains which tend to produce nssures in the heads of the rails.

5. A process for cooling rails from the original mill heat comprisingthe steps of cooling the rails from a temperature above the criticalrange at a s rate at least as rapid as that which normally occurs on thehot bed until the temperature of the rails is substantially below 500C., and preventing the `deveiopment of stresses and strains which tendto produce fissures in the heads of the rails by 'cooling slowly througha range of temperatures whichA includes the range 300 to 200 C., suchslow cooling being begun before the major mass of head metal of therails has cooled to 300 C. from the original mill heat, and being at arate considerably slower than the normal hot bed rate of cooling.

6. A process for cooling rails from the original mill heat, comprisingthe steps of cooling the rails from a temperature above the criticalrange at the rate which normally occurs on the hot bed until thetemperature of the rails is substantially below 500 C., and after suchcooling but before the major mass of the head metal has cooled below 300C. from the original mill heat enclosing the rails and cooling slowlythrough a temperature range which includes an extended range below 300C. to prevent the development of those stresses and strains which tendto produce fissures in the heads of the rails.

REGINALD B. GERHARDT.

